QSIG is a global signaling control standard for PINX-to-PINX (private integrated exchange) applications, intended for use in private networks to link multiple vendor PBXs by retaining feature transparency. QSIG provides services including completion of calls to busy subscribers, completion of calls on no reply, call forwarding/diversion, call interception, call intrusion, call offer, call transfer, call waiting, direct dialing in, do not disturb, six identification services, mobile services, multiple subscriber number, operator services, path replacement, recall and sub-addressing.
The European Commission charged the European Telecommunications Standards Institute for development and promotion of the QSIG access protocol. To date, QSIG capability has been a European Commission initiative and as such has a limited deployment domain (EC countries). For example, North American countries which utilize the ANSI standard or Pacific Rim counties which utilize NTT or DDI standards have been incompatible with QSIG. Deployment of the QSIG capability is dependent upon carrier and PBX vendor compliance with ETSI/ITU standards. Accordingly, the QSIG capabilities have been typically limited to countries wherein such standards are used.
Implementation of QSIG access protocols within existing network elements that are presently using non-ETSI/ITU standards encounters constraints including high cost to develop capability within non-ETSI/ITU switch elements, long time deployment cycle required (i.e., time to market delay), network integration costs are high both in time and money, administrative costs for maintaining multiple standards within a single network element are increased, minimal industry support for capability from non-ETSI/ITU countries, unable to achieve economies of scale (i.e., due to custom development), and risk if the product is not successful.
Referring to FIG. 1, a block diagram of a controlled protocol model for QSIG capability is depicted. The model is divided into three planes including call control, protocol control and signaling carriage mechanism. The call control entity communicates with peer call control entities to establish inter-PBX bearer channel connections between the two entities. The protocol entity provides services to the call control entity to facilitate the ability of the call control to send information flows to and receive information flows from peer call control entities. The signaling carriage mechanism provides services to the protocol entity for the transfer of messages. The signaling and bearer channels utilized to support QSIG capability are conveyed between appropriate network elements.
Referring to FIG. 2, a conventional network topology requires that a carrier use ETSI/ITU conforming network elements wherein external PBX communications access (i.e., voice and data) are controlled and managed by the ETSI/ITU conforming carrier. In addition, PSTN access is controlled and managed by the ETSI/ITU conforming carrier. PBX network elements have the appearance of being part of a single virtual PBX resulting from the feature transparency. When both the network and the PBX equipment conform to ETSI/ITU standards the virtual PBX model occurs because the vendors have signed a QSIG memorandum of understanding (MoU) and are committed to support the development, testing and inter-operability of the QSIG access protocols. Further, the network carrier supports the QSIG protocol standards that are required to allow the MoU client vendors to inter-operate.
There exists a need to provide improved devices and methods which utilize QSIG in other networks.